Aluminum alloy



tive quantities as follows Patented 1.1, 7-, 1931 UNITED STATES PATENTOFFICE HORACE CAMPBELL HALL, 01E LITTLEOVER, DERBY, AND TENNYSON FRASERBRAD- BURY,. OF DERBY, ENGLAND, ASSIG-NORS TO ROLLS ROYCE LIMITED, OFDERBY,

ENGLAND ALUMI U ALLOY No Drawing. Application filed September 30, 1930,Serial No. 485,548, and in Great Britain October 1, 1920.

This invention is a modification of the invention described inapplication for Letters Patent Serial No. 401,970, now Letters PatentNo. 1,782,300, of November 30, 1930, and the 51 modification thereofdescribed in our concurrentapplication'serial No. 485,547 of the date ofthis application. In thesaid application forLetters Patent we havedescribed an alloy compounded of the elements in the rela- Per cent ofthe whole Copper 0.5 to 5.0 Magnesium 0.1 to 1.7 Nickel; 0.2 to 1.5Iron; 0.6 to 1.5 Silicon exceeding 0.55 to 2.8 Titanium up to 0.3Manganese; up to 0.3 Aluminium the remainder Only traces'of otherelements.

In our concurrent application of the date of this application Serial No.485,547 we have described a modification of the said alloy in which themagnesium content exceeds 0.03 per cent but does not exceed 0.10 percent. Alloys falling within the saidranges are herei'nafter called thesaid alloys. 1

Since the date of our said application we have discovered that thecastings of the said alloys are more free from scum and pin holes,particularly on the upper surface, if a small quantity -of metallicsodium not exceeding 0.01 per cent of the alloy to be treated is plungedinto the alloy when in a molten condition, and preferably immediatelybefore the latter is poured into the mould. This process has the effectof cleaning and de-oxidizing the alloy.

dium is as follows: We take a small quantity of metallic sodium (notexceeding the aforesaid limit) and in order to'delay the oxidization ofthe sodium as long as possible wrap it ina piece of sheet aluminium oraluminium foil, and so wrapped plunge it into the molten alloy, and holdit below the surface thereof until it is diffused. The bulk ofthe sodiumso added is lost. through burning at the moment of immersion, andthrough the fluxing The preferred method of applying the soanddeoxidizing effect 'on the alloy, and only traces of 1t are left in thecastings. We are aware that it has previously been proposed to modifythe structure of aluminium alloys by the addition thereto of metallicsodium, but the proposals have been to add the sodium in quantitiesconsiderably larger than that which we use (namely not exceeding 0.01per cent of the alloy to be treated) which is insufficient to affect thestructure of the alloy but yet is suflicient to eifect the advantagesbefore described.

What we claim is 1. As a process in making a casting of the followingmetals, to wit:

Only traces of other elements.

before pouring the molten alloy into the mould, plunging into it a smallquantity of metallic sodium not exceeding 0.01 per cent of the alloy tobe treated.

2. A process as claimedv in claim 1 the metallic sodium being plungedinto the molten alloy immediately prior to the latter bein poured intothe mould.

3. A process as claimed in claim 1 the metallic sodium being held underthe surface of the molten alloy until diffused. i

In testimony whereof we have hereunto aflixed our signatures. I

HORACE CAMPBELL HALL.

TENNYSON FRASER BRADBURY. J

